Are Electric Boats Safe? Marine Fire Safety Technology Overview

One often cited risk to electric outboards and e-propulsion systems on the water is the potential fire hazard linked to the presence of energy storage systems onboard, notably lithium-ion batteries. There is no doubt that this is a valid concern, as water and electricity can be a deadly combination. In fact, the salt content of seawater causes it to be approximately 1 million times more effective at conducting electricity than fresh water. Anyone else remember that saltwater circuit class lab experiment from middle school? (Interestingly, pure distilled water with no minerals, salt, ions or other substances, actually does NOT conduct electricity.)

Mercury Avator Electric Outboard

Above: A Mercury Avator Electric Outboard motor. Photo via Lenny Rudow.

The Risk

As highlighted by the International Association of Fire Services (CTIF), numerous times, electric vehicles can be prone to spontaneously catching fire after being exposed to or submerged in salt water. The U.S. Coast Guard has also warned that saltwater exposure “can severely harm Lithium-Ion batteries, leading to a chemical reaction that creates a high fire risk”. Hence, maintaining optimal temperature for onboard lithium-ion batteries, keeping them away from saltwater and preventing overloading becomes paramount for safe operation.

Vision Marine 180E

Above: Vision Marine’s E-Motion 180-HP electric outboard engine. Photo by Vision Marine.

Fire Safety Features & Designs

Fortunately batteries and electronics have been on boats for many decades and modern boat manufacturers that are constructing vessels with electric propulsion systems onboard are taking this safety concern into account. Virtually all new electronic propulsion systems for boats are being designed with general boat fire safety top-of-mind. Numerous precautions, measures and design features are being implemented to protect the batteries and energy storage systems of an electric boat, just like any other boat. Let’s take a quick look at some of the key safety solutions and features builders are employing to help protect against the risk of fire.

Watertight Compartments

As the saying goes, the best way to stop a fire is to prevent it before it begins. In regards to safety and performance in the realm of electric boats, a prevailing trend among electric boat builders involves the implementation of watertight compartments carefully designed to provide a robust safeguard for onboard batteries, keeping them away from saltwater. This innovative design approach aims to counter the potentially detrimental effects of electrically conductive and corrosive saltwater, which can pose a substantial threat to the integrity and operational reliability of battery systems. Many of the batteries that are being utilized on these vessels actually come encased in waterproof enclosures themselves, such as the Torqeedo Power 24-3500 battery.

Torqeedo Battery

Above: The Torqeedo Power 24-3500 high performance lithium battery housing includes a BMS with safeguards against overcharging, short circuiting, deep discharging, polarity reversal or overheating and is waterproof to IP67, able to withstand water immersion in depths of up to 3 feet for up to 30 minutes. Photo by Torqeedo.

Watertight compartments, constructed within a boat’s structure, serve as a multi-layered defense mechanism against the ingress of saltwater. By enclosing the batteries in impermeable chambers, the boat builders ensure a formidable barrier that effectively isolates the sensitive battery components from the hostile marine environment. This isolation is crucial to preventing not only immediate damage but also the insidious, long-term corrosive effects that saltwater can exert on electrical components.

Forza X1 F-22 Electric Boat Charger

Above: A Forza X1 F-22 electric boat charging system. Photo by Forza X1.

Battery Cooling Systems & Smart Batteries

The protective measures don’t end with watertight enclosures alone. To further bolster safety and the effectiveness of these compartments, electric boat builders are utilizing advanced battery cooling technologies. Electric marine battery systems have the option of being cooled either through air cooling or liquid cooling, primarily employing a Battery Thermal Management System (BTMS), with liquid cooling being the prevailing approach. Within the BTMS, a fluid circulates through conduits, cold plates, and additional components that encase the battery cells, facilitating the transfer of heat to an alternate location, such as a radiator or heat exchanger. These fluid-carrying elements serve as a safeguard, inhibiting direct electrical contact between the cells and the cooling fluid.

Builders are also integrating “smart batteries”, as an effective approach for aiding in the reduction of potential fire hazards. This technology involves a sophisticated built-in cooling system that actively dissipates excess heat generated during battery operation, thereby preventing the accumulation of heat and reducing the risk of thermal runaway, which is a precursor to fire incidents.

By maintaining the batteries within a controlled temperature range, the likelihood of thermal issues leading to fires is substantially diminished. Consequently, the integration of liquid-cooled battery systems not only enhances the overall safety of the onboard energy storage but also bolsters the reliability and longevity of the batteries themselves, offering a comprehensive and prudent solution for fire risk management in the maritime context.

Battery Management Systems (BMS)

Modern Battery Management Systems (BMS’s) that are made up of an array of smart batteries with a central “brain”, all have built-in thermal regulation safeguards and charge differential monitoring systems that cause them to shut down before they rise above safe operating conditions and become a threat. An overloaded battery can quickly A proper BMS will keep each individual battery’s charge and temperature in the optimal state.

Garmin Screen Monitoring System Forza X1 F-22 Electric Boat

Above: The temperature monitoring system displayed on a Garmin screen onboard a Forza X1 F-22 electric center console boat. Photo via Forza X1.

These systems also address another very real fire hazard for electric boats: overloading. According to Captain Adam Goldberg, a firefighter in Tucson, Arizona who was interviewed by the local 13 News station there, “80% of the car fires they respond to are connected to overloaded batteries or bad installation.” The same risk holds true for boats and in particular, electric boats.

Motor Cooling

Beyond keeping the batteries cooled, electric motors are also liquid cooled or air cooled, or both. Manufacturers of electric outboards are employing various solutions in their products to keep the outboards operating at safe temperatures. Electric outboard manufacturer Elco builds all of their brushless PMAC electric motors with a built-in water-cooled system and a variety of preventative safety features including over-voltage and speed protections and alerts.

Forza Electric Boat

Above: A 2024 Forza X1 F-22 electric center console boat underway on the water with an electric outboard motor. Photo via Forza X1.

Key Takeaways

The integration of IPS67 and beyond watertight compartments, advanced battery management systems, sophisticated liquid cooling technology and real-time monitoring from the helm, combine to underscore an advancement in electric boat design technology and design. This fusion of protective elements serves not only to insulate onboard batteries from the corrosive influences of saltwater but also to ensure an elevated level of safety and peace of mind for boaters and electric boat owners.

Dual Torqeedo Deep Blue Motors

Above: Twin Torqeedo Deep Blue electric outboard motors on the transom of an electric boat. Photo via / Torqeedo.

As electric boat builders continue to refine and innovate these engineering solutions, the maritime community is poised to benefit from a new era of safer, more efficient, and ultimately more enjoyable electric boating experiences. The bottom line: a well-designed electric boat can be perfectly safe, just like a well-designed gas or diesel boat, provided it has been constructed with the above inherent fire risks in mind.

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